Seat recliner for reducing chucking

ABSTRACT

A locking pivot mechanism which may be used as a seat recliner to reduce chucking of a seat back has a toothed quadrant, a toothed pawl, and an engagement member. The engagement member is biased against the pawl which, in turn, is forced into engagement with the quadrant to lock the quadrant against rotation, thus reducing chucking.

This is a continuation of U.S. patent application Ser. No. 08/623,465,filed Mar. 28, 1996, now U.S. Pat. No. 5,622,410.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates generally to a locking pivot mechanism, and moreparticularly, to an adjustable seat recliner mechanism for reducingundesirable movement when the mechanism is locked.

Locking pivot mechanisms generally consist of a first pivoting memberhaving a plurality of teeth which is called a quadrant, and a secondtoothed member, called a pawl, adapted to lockingly engage the quadrant.The mechanisms are operable to lock the quadrant and restrict itsrotation, or to release the quadrant to allow it to rotate and to enablea seat back affixed to the quadrant to recline. The mechanism isselectively locked or released by manipulating the pawl, which ismounted for rotation between an engaged position where the teeth of thepawl and the quadrant mesh, and a disengaged position where the pawlretracts from and no longer meshes with the quadrant. When the quadrantand the pawl rotate, they define a first and a second center ofrotation, respectively. The quadrant and pawl generally mesh at a pitchpoint which is not on a line between the first and second centers ofrotation, so that when they are meshed, the quadrant is effectivelyprevented from rotating. Locking pivot mechanisms also may include adevice, such as a spring, for releasably urging the pawl to rotate fromthe disengaged to the engaged position, so that the default position forthe mechanism is a locked condition. U.S. Pat. Nos. 4,223,947;4,314,729; 4,406,497; 4,615,551; 4,765,681; 4,770,463; 4,709,965;4,801,177; 4,913,494; 4,591,207; 4,295,682; and RE 32,884 illustratesystems which utilize various pawl and quadrant engagement assemblies.

Another type of locking pivot mechanism includes a quadrant, a gear withtwo sets of teeth, a pawl, and an activating mechanism. Here, thequadrant engages one set of gear teeth and the pawl engages the otherset of gear teeth. The activating mechanism is activated which, in turn,moves the pawl from an engaged position, where the pivot mechanism islocked in place, to a disengagement position, where the quadrant is freeto rotate on the gear. Examples of such types of pivot mechanism areillustrated in U.S. Pat. No. 5,156,439; 5,150,632; and 5,205,609.

In reclining seats, the quadrant is mounted to an extremely long leverarm, namely the seat back, against which various forces are applied. Forexample, the locking recliner mechanism in a vehicle seat is quite smallwhen compared to the length of the reclining seat back, and vehiclevibration or movement of an occupant may impose various forces upon thatlever arm during use. These forces can impose a large moment about thequadrant when applied along such a lengthy lever arm, which can overcomethe capability of the mechanism to anchor the quadrant and seat back. Inaddition, any imperfections in the components of the pivot mechanism,such as play or backlash between the engaging teeth or tolerancesbetween the mechanism components, may allow the quadrant to move aminuscule amount even when the mechanism is locked. These smallexcursions are magnified by the length of the lever arm and becomenoticeable at the upper end of the seat. For example, the seat back ofan unoccupied seat may tend to oscillate when the vehicle encountersrough road conditions. Because the motion of the seat back is amplifiedby the length of the seat back frame, the vibration of the seat back canbe relatively large. This magnified play in a locking pivot mechanismhas been termed "chucking", and refers to any imperfection or play inthe mechanism components which allows movement of the quadrant and theattached seat back while the mechanism is in a locked condition.

One technique which has been employed to reduce chucking is to form thecomponents of the pivot mechanism with exceedingly close tolerances. Inother words, the corresponding teeth as well as the pivot bearings forthe rotating components may be manufactured with very high precision.This technique reduces play in the mechanism, and thus reduces chucking.However, manufacturing to such close tolerances is expensive, and closetolerances may bind the components of the system and prevent smoothoperation. The above disclosed patents illustrate ways to eliminate thisproblem. However, designers continue to strive to improve the art.

It is therefore desirable to construct a locking pivot mechanism whichis relatively small and simple, which operates smoothly without binding,and does not require excessively close tolerances, yet is capable oflocking the quadrant in a fixed position to inhibit play or excursions.

Accordingly, the locking pivot mechanism of the present inventionprovides a novel configuration to reduce chucking. The present inventionprovides a novel pawl quadrant and cam configuration with a biasingforce applied on the cam urging the pawl into contact with the quadrant.Also, in the present invention, the quadrant pivot center, pawl pivotcenter and pawl and cam contact point are located at the vertices of anequilateral triangle. These features enable firm engagement of the pivotmechanism and reduce chucking.

These and other advantages and features will become apparent from thefollowing description and claims in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a pivot mechanism arrangedaccording to the principles of the present invention, shown in a lockedconfiguration;

FIG. 2 is a top plan view of the pivot mechanism of FIG. 1; and

FIG. 3 is a side elevational view of the pivot mechanism of FIG. 1, withthe base plates and spring removed.

FIG. 4 is a view like FIG. 3 in a disengaged position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention generally provides a locking pivot mechanism whichmay be used as a seat recliner to reduce play, or chucking, of the seatback when the mechanism is locked. Referring in particular to thedrawings, FIGS. 1 through 4 show a locking pivot mechanism indicatedgenerally at 10 which includes a base plate 12 adapted to be affixed toa seat base (not shown), a quadrant 14 adapted to be affixed to a seatback (not shown), a pawl 18, and an engagement member 20 with a handle22. Quadrant 14 is mounted for rotation about a pivot pin 24 which isrigidly affixed to the base plate 12 and a cover plate 26. An inner end28 of a flat coil quadrant spring 30 is inserted within a slot 32 formedin the pivot pin 24, and the outer end 34 of quadrant spring 30 iswrapped around a quadrant pin 36 which is rigidly affixed to quadrant14, such that quadrant 14 is flexibly biased in a counterclockwisedirection, and the seat back (not shown) is urged in a forwarddirection. Quadrant pin 36 slides within an arcuate slot 38 formed as acut-out in cover plate 26, thus restricting quadrant 14 to a limitedangular range of motion.

Quadrant 14 is rotated about its center of rotation, indicated at point"A". The quadrant pin 24 passing through opening 48, in the quadrant 14,has a tight fit allowing for little, if any, play. In addition, gearteeth 42 are configured to have a pitch circle such that the teeth arenumerous and small. Also, the quadrant 14 has a triangular shape whichis rounded at its vertices with the teeth on the arcuate base 50 of thetriangle. Also, a mounting bracket 15 is attached to the quadrant 14 toattach the quadrant to a seat back.

A locking pawl 18 has a pawl pin 58 with ends which are mounted forrotation within a cover plate opening 62 and a base plate opening. Thepawl 18 is mounted for rotation about the pawl pivot pin center ofrotation, indicated at point "B", between an engaged position shown inFIG. 3, in which a plurality of pawl teeth 66 mesh with quadrant teeth42, and a disengaged position shown in FIG. 4, where pawl teeth 66retract from quadrant teeth 42 and enable pawl 18, and thus quadrant 14,to freely rotate. Because quadrant teeth 42 and pawl teeth 66 arerelatively small, pawl 18 is capable of making fine adjustments in thelocked position. Pawl 18 further has a thrust cam surface 68 which isadapted to be engaged by a cam surface 21 of a cam 40 of the engagementmember 20.

Engagement member 20 includes the handle 22, coupling portion 50, andthe cam 40. The coupling portion 50 includes an aperture 71 whichenables a pin 70 to rigidly affix the coupling portion to the base 12and cover 26. The engagement member 20 is pivotally mounted to the baseplate 12 and cover plate 26 to rotate in a counterclockwise engagingdirection or a clockwise disengaging direction. Also, the couplingportion includes a slot 77 which limits the movement of the engagementmember. A pin 79, which passes through cam 40, is in slot 77 to limitmovement of the engagement member 20. Cam 40 rotates about pin 79. Also,cam 40 has a cut out 41 which receives pin 43. Pin 43 is secured withthe coupling portion 50 and a spring 45 to provide a biasing force forengagement member 20. When engagement member 20 rotates in thecounterclockwise engaging direction, cam 40 is rotated, via pin 43 andspring 45, such that cam surface 21 pushes on thrust surface 68 of pawl18 at a contact point "C", to urge pawl teeth 66 to mesh with quadrantteeth 42 and to thereby inhibit rotation of quadrant 14. In thisposition, points A, B and C are located substantially at the vertices ofan equilateral triangle. When engagement member 20 rotates in thedisengaging clockwise direction, cam 40 rotates such that cam surface 21relieves thrust on cam surface 68 and allows pawl 18 to rotate in acounterclockwise disengaging direction, such that pawl teeth 66disengage from quadrant teeth 42 and allow quadrant 14 to freely rotateas seen in FIG. 4. The outer end 80 of spring 45 is rigidly affixed tobase plate 12 or cover plate 26, or both. Spring 45 flexibly biasesengagement member 20, and in turn cam 40, in the counterclockwiseengaging direction, such that cam surface 21 engages thrust surface 68of pawl 18 and urges pawl teeth 66 to mesh with quadrant teeth 42 andrestrict rotation of quadrant 14. The pivot mechanism of the presentinvention may of course utilize any appropriate type of biasing devicerather than coiled springs 30 and helical compression spring 45,including leaf springs, helical springs, or hydrodynamic biasingdevices.

In operation, the default position of the mechanism is shown in FIGS. 1and 3, in which spring 45 urges engagement member 20 and cam 40 in anengaging direction, pushing on thrust or cam surface 68 to urge pawl 18to also rotate in an engaging direction, thus causing pawl teeth 66 tofirmly engage quadrant teeth 42 and prevent rotation of the quadrant 14.Engagement member 20 and, in turn, cam 40 under the biasing force,automatically accounts for certain dimensional tolerances by urging pawl18 to mesh firmly with quadrant 14, regardless of those tolerances, thusreducing any backlash defined between pawl teeth 66 and quadrant teeth42 and thus inhibits movement of quadrant 14, and also the seat back(not shown). On the other hand, an operator may pull handle 22 upward,causing the coupling portion and cam 40 to rotate in the disengagingclockwise direction and alleviate the locking force imposed on thrust orcam surface 68. The rotation of engagement member 20 and cam 40 in thedisengaging direction is limited by slot 77, which prevents excessiverotation of engagement member 20 and prevents cam 40 from excessivelyretracting. Pawl 18 is then allowed to fall by the influence of gravityto the disengaged or released position shown in FIG. 4, such that pawlteeth 66 no longer mesh with quadrant teeth 42. Quadrant 14 with theseat back (not shown) may rotate, and the seat back (not shown) may bereclined or inclined to a desired position. The rotation of quadrant 14is of course biased in a forward counterclockwise direction by quadrantspring 30, and its angular range of motion is limited by quadrant pin 36and arcuate slot 38. After the position of the seat back (not shown) andquadrant 14 is adjusted, the operator may release handle 22, to enablespring 45 to rotate the engagement member and cam 40 in the engagingdirection to again lock the angular position of the pawl 18 and quadrant14 with the seat back (not shown).

According to the novel configuration of the present invention, spring 45is adapted to selectively push, via cam 40, on pawl 18 to urge it towardquadrant 14, thus reducing the distance between the quadrant center ofrotation at point "A", pawl center of rotation at point "B" and a pitcharc defined by pawl teeth 66, causing pawl teeth 66 and quadrant teeth42 to more firmly mesh. In particular, as best shown in FIG. 3, due tothe configuration of thrust surface 68 of pawl 18, the force exerted byengagement member 20 against pawl 18 can be represented by a vector "V"that is directed intermediate the pivot points A and B. This forcevector "V" is made up of its component vectors "X" and "Y" as shown. Aswill readily be appreciated by those skilled in the art, component forcevector "X" is directed substantially at pivot point "B". Accordingly,chucking of the seatback which is connected to the quadrant 14 issubstantially reduced. In addition, the "Y" component force vector isdirected substantially perpendicular to the interface between thelocking pawl 18 and the quadrant 15, thereby ensuring that the pawlteeth 66 firmly mesh with the quadrant teeth 42 which increases the loadcarrying capacity of the pivot mechanism 10.

The present invention therefore provides a locking pivot mechanism whichis relatively small and simple, yet is capable of locking the quadrantin a stationary position to restrict chucking of the quadrant when themechanism is locked.

It should be understood that the preferred embodiments of the inventionhave been shown and described herein, and that various modifications ofthe preferred embodiment of the present invention will become apparentto those skilled in the art after a study of the specification, drawingsand the following claims.

What is claimed is:
 1. A pivot mechanism for a vehicle seat,comprising:a quadrant adapted to be coupled with a seat back, saidquadrant being pivotally mounted about a first pivot and having a set ofteeth; a locking pawl having a first cam surface and a set of teethengaging said quadrant teeth for releasably locking said quadrant inposition, said locking pawl being pivotally mounted about a second pivotand moving from a first pawl position engaging said quadrant to a secondpawl position disengaging said quadrant enabling movement of saidquadrant; a cam member pivotally mounted on a third pivot and having asecond cam surface for engaging said first cam surface of said lockingpawl when said cam member is in a first cam position, said cam memberbeing biased in said first cam position so as to exert a locking forceon said locking pawl when said locking pawl is in said first pawlposition and movable to a second cam position enabling rotation of saidlocking pawl to said second pawl position, such that when said cammember is in said first cam position the locking force exerted againstsaid locking pawl creates a force vector that is directed between saidfirst and second pivots so as to substantially bisect a line extendingbetween said first and second pivots to thereby reduce the chucking ofthe seat back and ensure that the locking pawl teeth and quadrant teethfirmly mesh.